The research outlined in this proposal deals with several aspects of biologically active compounds produced by microorganisms. The main emphasis is on the biosynthesis of a number of antibiotics. The methods to be used include feeding experiments with precursors labeled with radioactive isotopes, but also to a large extent the use of 13C-labeled compounds in conjunction with 13C Fourier Transform NMR. Antibiotics to be investigated are pyrrolnitrin, chlorothricin, spectinomycin, dihydrophenylalanine, ketomycin, granaticin, and the naphthocyclinones. In addition, some structural work is proposed which involved the structure elucidation of carbomonensin, a biotransformation product of the antibiotic monensin. BIBLIOGRAPHIC REFERENCES: L. Zee, U. Horneman, H.G. Floss, "Further Studies on the Biosynthesis of the Antibiotic Indolmycin in Streptomyces griseus", Biochem. Physiol. Pflanzen (BPP) 168, 19 (1975). M.K. Speedie, U. Hornemann, H.G. Floss, "Isolation andCharacterization of Tryptophan Transaminase and Indolepyruvate C-Methyl transferase: Enzymes Involved in Indolmycin Biosynthesis in Streptomyces griseus", J. Biol. Chem., 250, 7819 (1975).